CSS and Menu Items

so I have the Menu IDs in my php so I can apply CSS to each menu item and am trying to make the text invisible. It works but when I add the code for item-3 the code gets applied to 4,5,6,7,8,9 also because they are subitems of number three. Any idea how to exclude the subitems?

.art-hmenu #menu-item-3 a
{
position: relative;
display: block;
overflow: hidden;
height: 36px;
cursor: pointer;
font-family: "Agency FB",Arial, Helvetica, Sans-Serif;
font-variant: small-caps;
font-size: 23px;
text-align: left;
opacity:.0;
filter:alpha(opacity=0);
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=0)";
filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=0);
}

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